Add intersection,intersectionWith for Data.Map #15
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hdgarrood
reviewed
Feb 14, 2019
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Looking good so far, just a couple of minor notes. I think adding these makes sense; intersection seems a little weird to me in terms of the amount of information it discards, and I don’t think I’ve ever wanted it, but intersectionWith seems more sensible at least, and also both of these functions already exist in Haskell’s containers library anyway.
src/Data/Map/Internal.purs
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| -- | Compute the intersection of two maps, preferring values from the first map in the case | ||
| -- | of duplicate keys. | ||
| intersection :: forall k a b. Ord k => Map k a -> Map k b -> Map k a | ||
| intersection = intersectionWith (\a b -> a) |
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Minor nit but I think it would be better to use const here.
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Ah yes ofcourse, fixed.
test/Test/Data/Map.purs
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| quickCheck $ \(TestMap m1) (TestMap m2) -> ((m1 :: M.Map SmallKey Int) `M.intersection` m2) == ((m1 `M.intersection` m2) `M.intersection` (m2 :: M.Map SmallKey Int)) | ||
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| log "intersectionWith" | ||
| for_ [Tuple (+) 0, Tuple (*) 1] $ \(Tuple op ident) -> |
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Is ident being used here?
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Nope, artifact from unionWith test this is based of. Removed.
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Not sure why these are missing.